Combs are familiar items of personal grooming. Before the late 1940's, combs were generally handcut from bone, wood or rubber. These combs were expensive because of the manual labor involved in individually carving out the teeth and subsequently polishing the combs.
For some time now it has been common practice to produce combs by injection-molding. The generally flat elongated structural features of combs, picks, lifts and the like make them suitable for manufacturing by the injection-molding process. First, a metallic mold, typically comprised of two complementary female halves, is made for the desired articles to be cast. The mold halves are then joined together and injected with a plastic to form the article. After the plastic has hardened somewhat, the mold halves are parted and the article is removed. Such molds can be used repetitively to mass-produce articles inexpensively.
However, the injection-molding process has some drawbacks and is not satisfactory in all respects. For example, a small amount of flashing is left on each molded article forming a mold-parting line where the mold halves are joined together. For most injection-molded articles the mold-parting line poses little or no problem. However, in the case of combs, the mold-parting line runs around the entire periphery of the article, including the free terminal ends of the teeth. Small but sharp burrs or ridges are formed where the parting line passes over the ends of the teeth which can scratch the scalp and cause discomfort.
To avoid these drawbacks, it is therefore desirable to smooth or enlarge and smooth the teeth ends. Modifying the mold to provide larger teeth ends still leaves a mold-parting line. Smoothing the teeth ends involves additional manufacturing steps and thus expense.
Hairbrushes with bristles having enlarged terminal ends formed by some kind of coating technique, have been available heretofore. However, the prior techniques for manufacturing such hairbrushes are not suited for use with molded, one-piece combs of high production volume and low unit cost. Hairbrush bristles are not usually manufactured using the injection-molding process and thus have no parting line nor its accompanying burrs and ridges. Injection-molded combs do have the parting-line problem. Heretofore, there has not been available a cost-effective technique for manufacturing combs having smooth enlarged teeth ends of good quality, durable construction, and pleasing appearance.
A need has thus arisen for a new and improved technique for inexpensively manufacturing molded combs with these features.